Shut-down apparatus for a string of photovoltaic panels

1. A shut-down apparatus for a string of photovoltaic panels electrically connected in series comprising: a plurality of control modules including an initial control module, one or more intermediate control modules and a final control module operatively associated to corresponding photovoltaic panels, each control module being adapted to cause the shut-down of a corresponding photovoltaic panel in response to a received input shut-down signal, said control modules being adapted to sequentially receive said input shut-down signals at subsequent shut-down instants, each pair of subsequent shut-down instants being separated by a corresponding time delay, the time delay being based at least in part on a time to accommodate a decrease in a voltage between power terminals of the corresponding photovoltaic panel to about a null value before said input shut-down signal is commanded for said subsequent control module such that shut-down of the subsequent photovoltaic panel occurs after the preceding photovoltaic panels have been de-energized.

2. The shut-down apparatus, according to claim 1 , wherein said plurality of control modules includes: said initial control module in communication with a control arrangement and with a subsequent control module, said initial control module being adapted to cause, in response to an input shut-down signal received from said control arrangement, the shut-down of a corresponding photovoltaic panel and provide an output shut-down signal for said subsequent control module, said output shut-down signal having a time delay with respect to the received input shut-down signal; each of said one or more intermediate control modules in communication with a preceding control module and with a subsequent control module, each intermediate control module being adapted to cause, in response to an input shut-down signal received from said preceding control module, the shut-down of a corresponding photovoltaic panel and provide an output shut-down signal for said subsequent control module, said output shut-down signal having a time delay with respect to the received input shut-down signal; and said final control module in communication with a preceding control module, said final control, module being adapted to cause, in response to an input shut-down signal received from said preceding control module, the shut-down of a corresponding photovoltaic panel.

3. The shut-down apparatus, according to claim 1 , wherein said plurality of control modules includes: said initial control module in communication with a control arrangement, said initial control module being adapted to cause, in response to an input shut-down signal received from said control arrangement, the shut-down of a corresponding photovoltaic panel; each of said one or more intermediate control modules in communication with said control arrangement, each intermediate control module being adapted to cause, in response to an input shut-down signal received from said control arrangement, the shut-down of a corresponding photovoltaic panel; said final control module in communication with said control arrangement, said final control module being adapted to cause, in response to an input shut-down signal received from said control arrangement, the shut-down of a corresponding photovoltaic panel; and said control modules being adapted to sequentially received said input shut-down signals from said control arrangement at subsequent shut-down instants separated by corresponding time delays.

4. The shut-down apparatus, according to claim 2 , wherein said final control module is adapted to provide, in response to an input shut-down signal, an output control signal having a time delay with respect to the received input shut-down signal.

5. The shut-down apparatus, according to claim 4 , wherein said final control module is in communication with a signalling module adapted to receive said output control signal from said final control module.

6. The shut-down apparatus, according to claim 1 , wherein each control module comprises a controller and a switching circuit controllable by said controller and electrically coupled in parallel with power terminals of a corresponding photovoltaic panel, said switching circuit being adapted to short-circuit the power terminals of said corresponding photovoltaic panel in response to a trip signal received from said controller, said controller being adapted to provide said trip signal in response to a received input shut-down signal.

7. The shut-down apparatus, according to claim 6 , wherein said switching circuit comprises a switch and an impedance electrically connected in series between the power terminals of said corresponding photovoltaic panel.

8. The shut-down apparatus, according to claim 6 , wherein said controller is adapted to provide, in response to a received input shut-down signal, an output shut-down signal having a time delay with respect to the received input shut-down signal; and wherein said plurality of control modules includes: said initial control module in communication with a control arrangement and with a subsequent control module, said initial, control module being adapted to cause, in response to an input shut-down signal received from said control arrangement, the shut-down of a corresponding photovoltaic panel and provide an output shut-down signal for said subsequent control module, said output shut-down signal having a time delay with respect to the received input, shut-down signal; each of said one or more intermediate control modules in communication with a preceding control module and with a subsequent control module, each intermediate control module being adapted to cause, in response to an input shut-down signal received from said preceding control module, the shut-down of a corresponding photovoltaic panel and provide an output shut-down signal for said subsequent control module, said output shut-down signal having a time delay with respect to the received input shut-down signal; and said final control module in communication with a preceding control module, said final control module being adapted to cause, in response to an input shut-down signal received from said preceding control module, the shut-down of a corresponding photovoltaic panel.

9. The shut-down apparatus, according to claim 6 , wherein each control module comprises a voltage sensor adapted to provide detection signals indicative of the voltage between power terminals of a corresponding photovoltaic panel.

10. The shut-down apparatus, according to claim 1 , wherein each time delay is a predefined value.

11. The shut-down apparatus, according to claim 1 , wherein each time delay is calculated depending, at least partially, on the voltage between power terminals of a corresponding photovoltaic panel during the shut-down of said corresponding photovoltaic, panel.

12. A control system for a photovoltaic plant, wherein it comprises a shut-down apparatus, according to claim 1 .

13. The shut-down apparatus, according to claim 3 , wherein said final control module is adapted to provide, in response to an input shut-down signal, an output control signal having a time delay with respect to the received input shut-down signal.

14. The shut-down apparatus, according to claim 13 , wherein said final control module is in communication with a signalling module adapted to receive said output control signal from said final control module.

15. The shut-down apparatus, according to claim 7 , wherein said controller is adapted to provide, in response to a received input shut-down signal, an output shut-down signal having a time delay with respect to the received input shut-down signal; and wherein said plurality of control modules includes: said initial control module in communication with a control arrangement and with a subsequent control module, said initial control module being adapted to cause, in response to an input shut-down signal received from said control arrangement, the shut-down of a corresponding photovoltaic panel and provide an output shut-down signal for said subsequent control module, said output shut-down signal having a time delay with respect to the received input shut-down signal; each of said one or more intermediate control modules in communication with a preceding control module and with a subsequent control module, each intermediate control module being adapted to cause, in response to an input shut-down signal received from said preceding control module, the shut-down of a corresponding photovoltaic panel and provide an output shut-down signal for said subsequent control module, said output shut-down signal having a time delay with respect to the received input shut-down signal; and said final control module in communication with a preceding control module, said final control module being adapted to cause, in response to an input shut-down signal received from said preceding control module, the shut-down of a corresponding photovoltaic panel.

16. The shut-down apparatus, according to claim 2 , wherein each control module comprises a controller and a switching circuit controllable by said controller and electrically coupled in parallel with power terminals of a corresponding photovoltaic panel, said switching circuit being adapted to short-circuit the power terminals of said corresponding photovoltaic panel in response to a trip signal received from said, controller, said controller being adapted to provide said trip signal in response to a received input shut-down signal.

17. The shut-down apparatus, according to claim 3 , wherein each control module comprises a controller and a switching circuit controllable by said controller and electrically coupled in parallel with power terminals of a corresponding photovoltaic panel, said switching circuit being adapted to short-circuit the power terminals of said corresponding photovoltaic panel in response to a trip signal received from said controller, said controller being adapted to provide said trip signal in response to a received input shut-down signal.

18. The shut-down apparatus, according to claim 4 , wherein each control module comprises a controller and a switching circuit controllable by said controller and electrically coupled in parallel with power terminals of a corresponding photovoltaic panel, said switching circuit being adapted to short-circuit the power terminals of said corresponding photovoltaic panel in response to a trip signal received from said controller, said controller being adapted to provide said trip signal in response to a received input shut-down signal.

19. The shut-down apparatus, according to claim 7 , wherein each control module comprises a voltage sensor adapted to provide detection signals indicative of the voltage between power terminals of a corresponding photovoltaic panel.

20. The shut-down apparatus, according to claim 8 , wherein each control module comprises a voltage sensor adapted to provide detection signals indicative of the voltage between power terminals of a corresponding photovoltaic panel.